Little bitty pythons like Balls only strike you for 2 basic reasons.
1. (a)A fear/defense response. It does pay to double check husbandry if this is the case. Temp's, high traffic insufficient hides(if your set up requires them), etc. The snake may just be "in a bad mood" and intolerant of handling at that time although, this seems pretty rare with any larger snakes. Hatchlings can be a different matter, they are tiny and lots of things see them as an easy meal so they can be defensive at this stage, by all means not all are, it is just a possibility.
1. (b) Sometimes something may just startle a snake and it will react with either a fight or flight response.
2. A mistaken feeding response. Most of us can tell you exactly what we did wrong when this is the case (although not always, that vid of the BP slowly deciding to gnaw on a thumb was both hilarious and confusing). A set of tongs that are used for only feeding is a great starting point(personally I do prefer forceps as I find them far more comfortable). Also a weight check on both the snake and prey items will help determine if the snake is being underfed(the feed schedule can also be altered to suit the individual snake, juveniles will eat more frequently than adults).
Most of the time observation and perseverance will result in you having a great relationship with what is for all intents and purposes a lovely "tame" wild animal.
Good luck and don't sweat it.